Highly Stable and Active Pt−Cu Oxygen Reduction Electrocatalysts Based on Mesoporous Graphitic Carbon Supports (original) (raw)

Supplemental information Characterization Nitrogen Porosimetry N 2 sorption analysis was performed on a Micromeritics Germini analyzer at-196 °C (77 K). The specific surface area was calculated using the BET method from the nitrogen adsorption data in the relative range (P/P 0) of 0.06-0.30. The samples were heated overnight at 100°C for degassing. The total pore volume was determined from the amount of N 2 uptake at P/P 0 = 0.95. The pore size distribution was derived from the adsorption branch of the isotherm based on the BJH model. Electron Microscopy Low-resolution images were visualized by TEM on a Phillips EM280 microscope with a 4.5 Å point-to-point resolution and operated at an 80 kV accelerating voltage. High resolution transmission electron microscopy (HRTEM) on the nanoparticles was performed using a JEOL 2010F TEM operating at 200 kV, and the carbon was imaged using a Hitachi HF-3300 at 300kV. Pictures were obtained at the optimum defocus condition. SEM-EDS was done to obtain average particle composition over a large area on a Hitachi S-4500 at 20 kV. X-ray photoelectron spectroscopy XPS was acquired using a Kratos AXIS Ultra DLD spectrometer equipped with a monochromatic Al X-ray source (Al Kα, 1.4866 keV) and operated with a 20 eV path energy for high resolution elemental scans and a160 eV for survey scans conducted at an angle of 45°. The sample was prepared by depositing the catalysts (1-2 mg) on the double sided copper tape and then placed into the vacuum chamber. Thermogravimetric analysis (TGA) TGA was conducted using a Perkin-Elmer TGA7 equipment under oxygen flow. Samples were heated to 750 °C at the rate of 25 °C/min. Samples were held at 50 °C for 10 min before increasing the temperature.